A Long Term Evolution (LTE) system is an important plan of the 3rd Generation Partnership Project (3GPP). When the LTE system adopts a conventional Cyclic Prefix (CP), a timeslot includes 7 downlink symbols with a certain length. When the LTE system adopts an extended CP, a timeslot includes 6 downlink symbols with the certain length.
FIG. 1 is a diagram illustrating a Physical Resource Block (PRB) in an LTE system according to a related technology. As shown in FIG. 1, one Resource Element (RE) is one subcarrier in one Orthogonal Frequency Division Multiplexing (OFDM) symbol, and one downlink Resource Block (RB) consists of 12 continuous subcarriers and 7 (6 in case of the extended CP) continuous OFDM symbols. An RB is 180 kHz in the frequency domain, and is one timeslot in the time domain. During resource allocation, resources may be allocated by taking two RBs (also called a PRB pair) on a sub-frame (corresponding to two timeslots) as a basic unit.
In an LTE system, the following physical channels are defined.
A Physical Broadcast Channel (PBCH): information carried by the channel includes: a frame number of the system, a downlink bandwidth of the system, a cycle of a Physical Hybrid ARQ Indicator Channel (PHICH) and a parameter Ng∈{⅙, ½, 1,2} for determining the channel group number of PHICHs.
A Physical Multicast Channel (PMCH): mainly configured to support a Multicast Broadcast over Single Frequency Network (MBSFN) service and broadcast multimedia time-frequency information to multiple users, wherein the PMCH may transmit data only in an MBSFN sub-frame and an MBSFN area.
A Physical Downlink Shared Channel (PDSCH): configured to bear downlink transmission data.
A Physical Downlink Control Channel (PDCCH): configured to bear uplink and downlink scheduling information and uplink power control information. PDCCHs in LTE Release 8 (R8), Release 9 (R9) and Release 10 (R10) are mainly distributed in first 1, 2, 3 or 4 OFDM symbols of a sub-frame, and specific distribution is required to be configured according to different sub-frame types and the number of Common Reference Signal or Cell-specific Reference Signal (CRS) ports. As shown in Table 1, Table 1 shows the numbers of OFDM symbols occupied by PDCCHs configured according to different sub-frame types and the number of CRS ports under the conditions that the number (NRBDL) of downlink Resource Blocks (RB) is more than 10 and not more than 10 respectively.
TABLE 1Number of OFDMNumber of OFDMsymbols occupiedsymbols occupiedby PDCCH underby PDCCH underthe conditionthe conditionSub-frameof NRBDL > 10of NRBDL ≤ 10Sub-frame 1 and sub-frame 61, 22in sub-frame type 2MBSFN sub-frame on a1, 22carrier supporting a PDSCH,CRS being configured tooccupy port 1 or 2MBSFN sub-frame on a22carrier supporting a PDSCH,CRS being configured tooccupy port 4Sub-frame on a carrier not00supporting PDSCHtransmissionNon-MBSFN sub-frame1, 2, 32, 3(except sub-frame 6 insub-frame structure type 2)configured to be a PositionReference Signal (PRS)All other cases1, 2, 32, 3, 4
A Physical Control Format Indicator Channel (PCFICH): information carried by the channel is configured to indicate the number of transmission OFDM symbols of a PDCCH in a sub-frame, and is sent on the first OFDM symbol of the sub-frame, and a frequency position of the PCFICH is determined by the downlink bandwidth of the system and a cell Identity (ID).
A PHICH: configured to bear Acknowledgement/Non-acknowledgement (ACK/NACK) feedback information of uplink transmission data, wherein the number and time-frequency positions of PHICHs may be determined by a system message in a PBCH of a downlink carrier where the PHICHs are located and the cell ID.
In order to improve spectrum efficiency more, a cell is deployed more and more densely, and user interference (as shown in FIG. 2) in the same cell and co-channel interference (as shown in FIG. 3) between cells increasingly become main factors which limit network capacity.
In current researches, interference compression is implemented on a sending side mainly in manners of pre-coding, cooperative scheduling and the like on a network side. However, such network-side-based interference cooperation greatly depends on accuracy of fed Channel State Information (CSI). Related research data show that an advanced receiving method may also be adopted to well compress interference. In addition, compared with interference cooperation in the sender, terminal-based enhancement may alleviate pressure from channel information feedback. Therefore, how to optimize terminal reception for better interference compression is an important direction for effectively improving spectrum efficiency.
In an LTE R8 system, a CRS is adopted for Channel Quality Information (CQI) measurement and channel demodulation of a PDCCH/PDSCH. Since a CRS is a cell-specific signal, all terminals of the same cell adopt the same CRS resource. Resources occupied by CRSs of different cells may be staggered, that is, different cells have the same Vshift value. The resources occupied by the CRSs of different cells may also be completely overlapped, that is, different cells have different values. Herein, Vshift is related to a cell ID NIDcell, and is consistent with Vshift=NIDcell mod 6. FIG. 4 and FIG. 5 are diagrams (Vshift=0) illustrating CRS resource configuration under normal CP and extended CP conditions respectively. When a CRS-based pre-coding processing manner is adopted, a sender is required to additionally notify a receiver of pre-coding weight information adopted during data transmission, and pilot overhead is higher. In addition, in a Multi-user Multi-input Multi-output (MU-MIMO) system, multiple users adopt the same CRS resources, so that it is impossible to achieve orthogonal pilot, thereby limiting target data channel estimation performance under a multi-user transmission condition.
In order to reduce pilot overhead and improve channel estimation accuracy, pilot measurement and data demodulation functions are separated in an Advanced Long Term Evolution (LTE-A) system, and two types of reference signals are defined respectively: a Demodulation Reference Signal (DMRS) and a Channel State Information Reference Signal (CSI-RS). A DMRS is mainly configured to implement channel estimation of a PDSCH and an Enhanced Physical Downlink Control Channel (ePDCCH) for data/control channel demodulation, and pre-coding information of the corresponding PDSCH/ePDCCH is contained during transmission of the DMRS. A CSI-RS is mainly configured to implement channel measurement to obtain and feed back CQI to enable a Node B side to implement a user schedule and implement adaptive allocation of a Modulation and Coding Scheme (MCS) by virtue of the CQI, and pre-coding information is not contained during transmission of the CSI-RS. CSI-RSs also includes a type of special CSI-RSs called Zero Power Channel State Information Reference Signals (ZP-CSI-RSs) and determined as zero power signals sent on resources for the ZP-CSI-RSs. A ZP-CSI-RS is mainly intended to ensure orthogonal CSI-RSs between cells and avoid interference between the CSI-RSs of the cells and a PDSCH. In addition, in an LTE Release (R11), a Channel State Information Interference Measurement (CSI-IM) signal is introduced, and is mainly configured to improve CQI interference measurement performance.
However, there is yet no effective solution for how to improve interference measurement performance under a PDCCH/ePDCCH/PDSCH demodulation condition.